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Rab Proteins

Rab Proteins

Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...

Rab Cascades

Rab Cascades

Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.

Small GTPases - Ras and Rho

Small GTPases - Ras and Rho

Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:

GTPases and their Regulation

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...

GTPases and their Regulation

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...

Activation and Inactivation of G Proteins

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...

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Related Experiment Video

Updated: May 16, 2026

Comparing the Affinity of GTPase-binding Proteins using Competition Assays

Comparing the Affinity of GTPase-binding Proteins using Competition Assays

Published on: October 8, 2015

Analysis of rab GTPases.

Lars Langemeyer¹, Francis A Barr¹

¹Department of Biochemistry, University of Oxford, Oxford, United Kingdom.

Current Protocols in Cell Biology

|December 5, 2012

Summary

This study details methods to identify proteins regulating Rab GTPases, crucial molecular switches in membrane trafficking. These techniques characterize Rab GTPase regulators like GEFs and GAPs, essential for cellular signaling.

Area of Science:

Molecular Biology
Cell Biology
Biochemistry

Background:

Rab GTPases are key regulators of membrane trafficking, functioning as molecular switches.
Their activity is modulated by GDP-GTP exchange factors (GEFs), GTPase activating proteins (GAPs), Rab chaperones, and effector proteins.

Purpose of the Study:

To describe methods for identifying proteins that interact with and regulate Rab GTPases.
To provide tools for characterizing the functions of Rab regulatory proteins.

Main Methods:

Methods focus on identifying and characterizing the interactions between Rab GTPases and their regulatory proteins.
Techniques allow for the assessment of GEF, GAP, chaperone, and effector protein activities.

Main Results:

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Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay

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Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells

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Last Updated: May 16, 2026

Comparing the Affinity of GTPase-binding Proteins using Competition Assays

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Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay

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Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells

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The described methods enable the identification of specific proteins associated with Rab GTPase regulation.
These methods facilitate the assignment of regulatory proteins to their cognate Rab GTPases.

Conclusions:

The presented methods are valuable for dissecting the molecular mechanisms of Rab GTPase signaling.
These techniques are essential for understanding the specificity of membrane trafficking control.